Silicon–germanium films for photomasking applications

Abstract

Si–Ge films have been deposited by RF co-sputtering and have been compared to Cr films for use as opaque materials on photomasks. One of the potential attractions of Si–Ge is its ability to be patterned by dry etch, anisotropic processing. Optical absorption coefficients were measured from 347 to 820 nm using a modified spectrophotometer. The absorption coefficient of Si–Ge films (containing 32.6% Ge) was 1.5 × 10⁵ cm^–1 whereas the ‘standard’ Cr gave 5.6 × 10⁵ cm^–1. A simple scratch test was used to compare the adhesion of the films to fused silica substrates. Specially fabricated cantilevers were used to study interfacial stress between films and substrates. Cr and Si–Ge with similar thicknesses exhibited tensile and compressive stress, respectively. These observations have confirmed the potential of Si–Ge as a photomask opaque.